According to the Pentagon, the US has already declared war on Iran

WASHINGTON—The Pentagon has concluded that computer sabotage coming from another country can constitute an act of war, a finding that for the first time opens the door for the U.S. to respond using traditional military force.

The Pentagon's first formal cyber strategy, unclassified portions of which are expected to become public next month, represents an early attempt to grapple with a changing world in which a hacker could pose as significant a threat to U.S. nuclear reactors, subways or pipelines as a hostile country's military.

In part, the Pentagon intends its plan as a warning to potential adversaries of the consequences of attacking the U.S. in this way. "If you shut down our power grid, maybe we will put a missile down one of your smokestacks," said a military official.

So, ah, when somebody else does it to us, that's effectively a declaration of war, right?

The New York Times reported that President Barack Obama secretly ordered cyber warfare against Iran to be ramped up in 2010 after details leaked out about Stuxnet, which some say came from the US, Israel or both.

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"Large nations with large spy agencies have been using these kinds of techniques for more than a decade," said James Lewis, a senior fellow who monitors technology at the Center for Strategic and International Studies in Washington.

Lewis said cyber espionage is "not a weapon" but can be "very effective" as an intelligence tool and can avoid some of the problems with traditional surveillance such as spy planes.

"If you have to choose between this and a pilot being paraded through the streets of Tehran, this is much preferable," he said.